The present invention relates to a unit for transferring cigarette sticks from a cigarette maker to a filter tip attachment.
The term “cigarette maker” describes a machine by which at least one continuous cigarette rod is fed at a substantially steady rate into a filter tip attachment, advancing along its own axis.
Passing through the outfeed of the cigarette maker, the continuous cigarette rod encounters a cutter head by which it is divided up into sticks normally of “double” length, that is to say, sticks measuring twice the length of a stick that will be joined ultimately with a respective filter tip to create a standard filter cigarette.
After the cutting step, the cigarette sticks continue to advance axially, pushed forward by the continuous rod behind, to the point of reaching a transfer position where each one is engaged by transfer mechanisms operating between the outfeed stage of the cigarette maker and an infeed device of the filter tip attachment. The infeed device in question takes the form of a roller rotatable about an axis parallel to that of the cigarette rod and furnished with a succession of aspirating seats or channels around the periphery, extending parallel to the rod and capable of movement in a direction transverse to their own axes and to the axial feed direction followed by the rod.
Conventional transfer mechanisms consist in an impeller type device comprising one or more rollers of which the function is to distance the sticks one from the next and guide each one into a relative channel of the infeed roller.
It will be clear that when entering the relative channels of the transfer mechanism, the sticks must decelerate to zero linear velocity in the axial direction and accelerate to the angular velocity of the roller in the transverse direction.
The single sticks are slowed to a halt by suction means incorporated into each of the channels.
Such means comprise a plurality of holes arranged along the bottom of each channel and connected to a source of negative pressure.
Sliding into the respective channel and engaging the suction holes one by one, the stick is made to advance progressively slower in the axial direction while being diverted in the transverse direction at the angular velocity of the roller.
The aspirating channels present a splayed profile at the entry end, thereby facilitating the passage of a relative stick onto the bottom of the channel, with which it makes contact along a straight line generator.
It will be evident that as the cigarette stick is taken up by the respective channel, the portions of the cylindrical surface of the stick exposed to the aspirating force are limited to the areas engaging the mouths of the suction holes.
The holes are typically three or four in number, each approximately 4 mm in diameter, and given the high axial velocity at which the cigarette sticks are caused to advance in filter tip attachments of recent design, it is essential that notably high values of negative pressure are generated in order to ensure that the sticks are retained swiftly and securely, especially at the moment of entering the channel, and apply a similarly swift and effective braking action to the stick as it advances along the channel. If not, the speed of entry on reaching the bottom of the channel will be likely to damage the stick and/or cause the tobacco filler to shed from the ends.
Also, because of the way the aspirating channels in question are fashioned currently, considerable pressure losses occur along the entire length of the channel and around the suction holes.
To overcome such problems, the prior art embraces the solution of using high power suction equipment in conjunction with pneumatic circuits that are rendered notably complex and costly as a result of being specified with ultra high strength pipelines and seals, the effect of which being to generate high electrical power consumption and high noise levels in the pneumatic circuits as the sticks enter the relative channels.
The object of the present invention is to provide a unit for transferring cigarette sticks from a cigarette maker to a filter tip attachment such as will be unaffected by the drawbacks mentioned above in referring to the prior art.